The way of trial plan is called "the best mixed plan", for it contains the idea of combination plan and uses the fundamentals of the best plan, it is close to two kinds of plans. The highest output of silt arrested land plot 1998, 1999 and 2000 reaches 12 919.5 kg·hm -2 , 13 815.0 kg·hm -2 and 15 018.0 kg·hm -2 respectively. There are 343 plans obtained through computer, the best combination plan with yield of 15 000～17 625 kg·hm -2 is to use 60 000 kg·hm -2 of organic manure, 462～483 kg·hm -2 of N, to irrigate 600 t·hm -2 of water before seeding, 1 377～1 458 t·hm -2 of water in crop growth, to maintain the density of potato and sorghum with 72 705～83 415 per hm 2 and 65 205～75 915 per hm 2 respectively.